Froome (left) with team-mate Thomas, following eventual stage winner Vuillermoz on the Mur de Bretagne

Chris Froome held on to the yellow jersey after stage eight of the Tour de France from Rennes to Mur de Bretagne.

Team Sky's Froome, 30, finished eighth as Alexis Vuillermoz became the first French stage winner of this year's race on a steep climb to the finish.

Ireland's Dan Martin was second with Spain's Alejandro Valverde third.

Defending champion Vincenzo Nibali lost 10 seconds to Froome on the final 2km climb but Nairo Quintana and Alberto Contador finished alongside the Briton.

"That was a tough climb, but my team-mates did a great job in bringing me to the front, I was in the best position," said Froome after retaining his 11-second lead over Slovakia's Peter Sagan, who finished fourth.

"I was quite surprised to hear that I gained some time on Vincenzo Nibali."

Froome was again expertly looked after by Geraint Thomas as the peloton upped the pace in the run-in to the bottom of the final ascent.

The narrowing roads meant space was at a premium and each of the leading teams was keen to keep their riders towards the front of the bunch to put them in the best position to attack and avoid crashes.

Thomas had Froome tucked in behind him as they started the climb which featured gradients of 15% in the opening kilometre.

As Thomas dropped away, Froome found himself briefly at the head of the race but AG2R rider Vuillermoz attacked about one kilometre from the finish and stayed clear to win by five seconds.

Analysis - BBC Sport's Matt Slater

"The scenes behind the finish atop the Mur de Bretagne can only be described as chaos: glorious, confusing, happy (for the most part) chaos. The hordes of Bretons who walked or rode up the 2km hill this morning were treated to the spectacle of a French win. OK, Alexis Vuillermoz is from the Jura, so not a local, but French winners have dried up since Brittany's Bernard Hinault was in business, so all are welcome.

"Peter Sagan was smiling, too, back in green, and Chris Froome continues to grin his way to the race's real battlegrounds in the mountains. Less happy were Ireland's Dan Martin, boxed in at the crucial moment and unable to follow the winning move, and the numerous riders asked by the UCI to hand in their bikes for spot checks for hidden motors. It was a long walk back to the buses."

Sagan's fourth place earned him enough points to take the green jersey from Germany's Andre Greipel. The Slovakian leads on 213 points with Greipel on 210 and Britain's Mark Cavendish third on 159.

Geraint Thomas's stage-by-stage guide

Stage nine: Vannes - Plumelec, 28 km (17.4 miles)

"The tactics for a team time trial are simple: ride as fast you can and get the fifth guy over the line as quickly as possible because that is when the clock stops and all the riders in your team get credited with that time."It's a bit different to a normal team time trial because the profile is quite lumpy, and after eight days of hard racing there'll be a few teams who don't start with nine riders but six or seven. When you have to finish with five that will make it harder again."

Britain's Adam Yates, who finished seventh, "tried following Vuillermoz" but "had nothing left". However, the Orica GreenEdge climbing specialist said he is waiting "to see what he can do" when the race reaches the Pyrenees mountains on Tuesday.

Before that, there is Sunday's 28km team time trial from Vannes to Plumelec which could further shake up the standings because the time credited to each rider is taken when the fifth in each team crosses the finish line.

"You need five riders to get up that final climb together," said Froome. "That's going to make it quite tough for a lot of teams. I do expect there to be quite substantial time differences."

American Tejay van Garderen, who is third overall, 13 seconds behind Froome, could take the race lead as his BMC Racing squad is strong against the clock.

There will be live text and radio commentary of the team time trial on the BBC Sport website from 14:00 BST.

Britain's Adam Yates (right) tried to follow Vuillermoz when he attacked on the Mur de Bretagne

Froome will wear the race leader's yellow jersey in Sunday's team time trial

Nibali's hopes of defending his Tour de France title took another blow on Saturday